A Little Experiment
by TheMadKatter13
Summary: [TTF 50/SWN 05] Anonymous said: For your taboo request - Holmescest tentacle porn where one person uses a tentacle to pump the other full of eggs. Bonus points if you describe the sensations of the eggs in detail. AU; Adult Tentacle Mycroft / Shota Human Sherlock


**SUMMARY: Anonymous said: For your taboo request - Holmescest tentacle porn where one person uses a tentacle to pump the other full of eggs. Bonus points if you describe the sensations of the eggs in detail.**

 **AO3 TAGS: Alternate Universe, Eldritch, Tentacles, Creature Mycroft, Tentacle Mycroft, Adult Mycroft, Human Sherlock, Underage Sherlock, Shota Sherlock, Tentacle Sex, Tentacle Rape, Rape/Non-con Elements, Sex, Underage Sex, Anal, Anal Sex, Loss of Virginity, Virgin Sherlock, Top Mycroft, Bottom Sherlock, Impregnation, Oviposition**

 **AN: Another NOTP but, you know, anything for The Spite.**

 **Brought to you by them sexy Elder Gods in Hellboy.**

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 _"Would you like to conduct a little experiment, Sherlock?"_

Sherlock was still young, even by human standards, and there was much he didn't know. Which meant he was still susceptible to Mycroft's machinations in the pursuit of all knowledge. All Mycroft had had to do was offer Sherlock something of interest, and his little brother had played right into his hands. Or rather, his tentacles.

On the bed, Sherlock whimpered and tried to shift, but Mycroft had him wrapped tight in his myriad of copper limbs Tentacles that Sherlock wouldn't achieve until he'd hit puberty - Mycroft was already betting they'd be a soft grey, like Sherlock's eyes.. Until then, his little brother may as well have been human. He was certainly as weak as one, and couldn't fight the prehensile limbs holding him naked and spread-eagle on the bed.

"Mycroft!" Sherlock shouted. Or he tried to. The word was muffled from the tip of the tentacle gagging him, keeping him from shouting out and alerting any of the housekeepers, but not either of their parents, away on vacation for the summer months. Mycroft smiled as he shifted on the mess of tentacles keeping him aloft from the floor, lifting his hand to take a deep inhale of his cigarette.

"Don't fear, little brother," Mycroft comforted, exhaling smoke and stroking the wet tip of his penile tentacle over the tight furl of a virgin arse. Well, not for much longer.

Sherlock screamed around Mycroft's tentacle when Mycroft breached him, his throat vibrating around Mycroft's limb and making him shudder with the pleasure of it, making the fag between his fingers tremor. The feel of the wet heat convulsing around the tentacle in Sherlock's arse only heightened the sensations.

"Don't be afraid, Sherlock," Mycroft said again, pushing deep, coiling his length into the small boy. "You won't need to hold the eggs for long."

"Uh-uhh?" Sherlock managed to hum, eyes widening. He was such a pretty boy. He would have no trouble attracting a mate when he became of age. Not physically, anyway. His personality would do him no favours.

"Eggs," Mycroft confirmed, slowly fucking into the warm body with his penile limb, sedately taking drags of his cigarette. Perhaps later, he'd be able to indulge and play a little bit, give all of his tentacles time inside Sherlock, but his brood came first. "It's time to lay my clutch, and the eggs require a body to incubate them. In a matter of weeks, you'll be able to lay them where the may grow to their full size before hatching. Lucky for you, you have a great deal of reading to catch up on that you'll now have all the time for."

His adorable little brother cried out again, squirming on Mycroft's tentacle, which only made him push into the boy harder, aroused by the additional stimulation. He curled the tip and Sherlock jerked arching up from the bed, eyes going wide as his previously soft cock, small and pink twitched and began to swell. Sherlock shook his head, but it was far too late, and his writhing only further served to drive Mycroft's arousal higher.

There had been no lust to initiate this, only practicality, but that did not stop the pleasure from rising in Mycroft's belly. His biology only required him to lay a clutch every century or so, and this was only his second one, but this experience was already vastly improved to the first one. Sherlock's young human body certainly helped, the almost-unbearable tightness, the heat, the way he could barely seem to lay still as he experienced sex for the first time, always struggling against Mycroft's tentacles and whimpering and moaning around the one in his mouth. He felt… good. Almost too good.

Mycroft groaned as the first egg traveled down his length. He could see the bulge of it, and Sherlock apparently could too, his grey eyes widening as they followed the path closer to his body. He shouted and he struggled, trying to break away, but he couldn't. The egg stopped at the tight ring of his sphincter, but Mycroft forced it through, into the body that would be housing it for the next few weeks. Sherlock _screamed_ , his body arching in a clean bow off the bed, his small cock still too young yet to produce sperm, but the pressure on his prostate would have been unbearable, inconceivable. When it had finally settled into his body, his belly bulging with it, Sherlock settled back to the bed, body trembling and eyes leaking tears.

"You took your first egg well, Sherlock," Mycroft praised, stubbing the butt of his cigarette out on his hand and dropping it to the floor to be picked up later. He wiped dusted the smudge of ash on his palm on the hem of his suit jacket, and then lit another.

"Mmm mmm?" Sherlock mumbled through the obstruction in his throat, eyelashes and cheeks wet.

"Of course," Mycroft confirmed. "I did say I had an entire clutch. And look, here comes the next."

Once again, his precious little brother struggled and screamed, and again, it was to no avail. This time, however, Mycroft shifted forward on his tentacles to press a palm to Sherlock's belly, and he hummed at the sensation of not only pushing his egg into his brother's small body, but also in feeling the skin under his hand swelling with his clutch. He gave no quarter this time, and continued to pump his eggs into his little brother, pleased at the lumpy shaping of Sherlock's stomach under his hand.

Where as the last time he delivered a clutch, he'd had seven eggs, this time he had nine, and his brother's small body was positively distorted by the eggs he now carried. "And now, to fertilize them," he murmured, though Sherlock could no longer hear him. His eyes had become glazed during the third egg, and his attempts at words had become meaningless whimpers, his struggles indirectional squirming.

Mycroft's penile limb pulsed inside of his brother, the curves of his clutch a novel and arousing situation, one that had his orgasm rising quick and hot in his belly. He hummed as he came, his seed coating the inside of his brother and the eggs he'd filled him with. It took some time for his release to finish, but by the time it did, the uneven swell of Sherlock's stomach had evened into a smooth curve, a balloon of eggs and semen.

"Very good, Sherlock," Mycroft murmured, curling his 'cock' into a knot to keep his seed inside his brother. He stroked over Sherlock's stomach, calming sweeps of his hand to keep his brother still and high on the sensation of being so full. "You did quite well receiving your first clutch. I would declare this experiment a rousing success with a positive probability of an equally successful repeat."

Of course there was no answer, but Mycroft didn't mind. He stubbed out his dying cigarette and lit another fresh one, and settled in for the lengthy wait. Smoke filled his lungs and the sound of Sherlock's trembling breaths filled his ears. In the silence of their nearly-empty house, Mycroft took up his post at his little brother's side and set to running his fingers through the soft curls.

"I'm sorry to have immobilized you for the coming weeks," he told Sherlock's unconscious body with a soft smile he didn't dare to show when Sherlock was awake to rebuke his affection. "But you'll understand when you're older."

FIN

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 **Since this was Mycroft's POV… maybe half bonus points for the egg-sensation detail? lol**

 **Like the thing? Reblog the thing (** **themadkatter13fanfiction tumblr, /tagged/A-Little-Experiment).**


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